The present invention relates to the production and propelling of solid sublimable particles. The machine comprises at least:
a system for producing or calibrating sublimable solid particles; and
a system for receiving said sublimable solid particles and for moving said particles to an outlet for ejecting or blasting sublimable particles.
Such a system is suitable for an easy cleaning of inaccessible parts without additional residues.
In the present specifications, the wording xe2x80x9csublimable solid particlesxe2x80x9d means particles made of a material that permits sublimation at the temperature and pressure of the object to be cleaned, on which said particles are propelled or blasted. These particles are advantageously made of solidified gas at a temperature lower than 20xc2x0 C., in particular lower than 0xc2x0 C., preferably at a temperature lower than xe2x88x9220xc2x0 C. Those particles are for example particles of CO2 or containing solid CO2.
EP-A-07689334 (corresponding to U.S. Pat. No. 5,520,572) discloses a machine to produce and propel sublimable solid particles on demand. The machine comprises a horizontal chamber containing CO2 blocks, a mechanical pushing mechanism, a granulation system with long knives, a transmission to have them turning in a vertical plane, a mechanical feeding system pushing CO2 pellets on the granulation system, a duct to bring the particles to a distributor conveying the particles in a duct provided with a propelling gas feeding, and an exhaust nozzle mounted on the end of the latter duct.
In this machine, knives act on blocks of solid CO2, for cutting solid CO2 slices which are converted or broken into granules of variable size or length. This machine is also very expensive, as it required a system for pushing horizontally the blocks of CO2 on the knives. This machine is also too heavy to be carried by a person on his back.
Furthermore, the EP-A-0768934 machine also cannot work in a continuous way, as the pushing system must be removed for refilling the chamber with CO2. For limiting the refilling problem, the chamber has a high volume so as to have a sufficiently long working time, this rendering the machine heavy.
Finally, as only slices of material are cut during the working of said machine, it means that a large portion of the particles do not have a sharp edge, such an edge being advantageous, for example, for a specific cleaning operation, such as the cleaning of paint.
U.S. Pat. No. 5,071,289 (corresponding to WO9109800) discloses a system for moving particles by means of a blasting gas, said particles issuing from a hopper provided with a stirring means. Such a system can be used for propelling sublimable solid particles. This document does not disclose the preparation of the solid particles to be blasted out.
The present invention relates to a machine having one or more advantages with respect to the system of the state of the art. Said advantages will be disclosed hereinafter.
A first object of the invention is a system for producing and propelling solid sublimable particles, said system comprising at least:
a first means for producing solid sublimable particles;
a second means connected to said first means, said second means receiving solid sublimable particles produced by said first means and propelling said solid sublimable particles towards an outlet, and
at least one duct extending between the first means and the second means for conveying solid sublimable particles produced by the first means to the second means,
In the system of the invention, the first means for producing solid sublimable particles comprises:
a container with a first opening adapted for receiving solid sublimable material and a second opening associated to a cutting plate having a face indented to be directed towards the solid sublimable material present in the container and intended to be in contact with said solid sublimable material present in the container, said face being provided with at least one line of teeth associated to at least one passage extending through the cutting plate,
means for driving into rotation the cutting plate;
whereby the cutting teeth of the cutting plate driven into rotation are adapted for producing, when contacting solid sublimable material present in the container, solid sublimable particles with an average diameter smaller than 6 mm.
Advantageously, the plate forms at least partly a bottom for the recipient intended to receive sublimable material, so that said sublimable material present in the recipient is at least moved towards the plate by gravity.
Preferably, the plate is provided with teeth adapted for shaving the sublimable material present in the container into sublimable particles with an average size comprised between 0.1 mm and 5 mm, for example an average particle size between 0.5 and 4 mm.
Preferably, the plate is provided with a series of independent teeth or teeth which are distant from each other, whereby a better control of the size of the particles can be obtained. The maximum size of the particles can thus be controlled by selecting teeth with appropriate cutting edge and section of passage through the plate.
By using two or more different types of teeth, it is possible to produce a mixture of particles comprising two or more different fractions of particles, said fractions having different mean particle sizes.
According to an embodiment, the plate forms at least partly a bottom for the recipient intended to receive sublimable material, so that said sublimable material present in the recipient is at least moved towards the plate by gravity, and in which the plate is provided with teeth adapted for shaving the sublimable material present in the container into sublimable particles with an average size comprised between 0.1 mm and 3 mm. Most preferably, the solid sublimable material is substantially only moved towards the plate by the force of gravity. In the preferred embodiment, there is no mechanical means for pushing the solid sublimable material towards the plate, whereby during the working of the system, the container can be refilled, making continuous work possible.
According to a detail of an embodiment, the plate is substantially circular and is provided with a series of lines with teeth, each line of teeth extending substantially along a radial direction of the substantially circular plate.
According to another detail of an embodiment, the teeth have a free cutting line extending above the face of the plate intended to be in contact with the sublimable material present in the container, said free cutting line having a shape selected among the group consisting of U-shape, V-shape, a triangle, a square, a rectangle, a half hexagon, a half trapeze, a half octagon, a half pentagon, a half ellipse and combination of these shapes, said teeth being provided with means for guiding the formed particles towards the passages provided in the plate.
Preferably, the plate has at least one line of teeth adapted to form particles with a shape having at least one sharp edge.
According to a specific embodiment, the plate is provided with at least a first series of teeth and a second series of teeth, the teeth of the first series defining a first series of circular working paths during the driving into rotation of the plate, while the teeth of the second series defines a second series of circular working paths, at least one circular path of the second series being located between two adjacent circular working paths of the first series.
Preferably, in this embodiment, the plate is provided with sufficient teeth with different circular working paths, whereby the plate has a substantially continuous teeth working zone corresponding to a major portion of the face of the plate intended to be in contact with the sublimable material present in the container.
According to an advantageous detail of an embodiment, the system further comprises at least a scraping means working with the plate. For example, the system further comprises at least a scraping means working with the face of the plate intended to be in contact with the sublimable material present in the container.
The teeth of the plate are made to produce particles, with an average diameter below 6 mm, from the original sublimable solid material or blocs present in the recipient. The teeth are made to permit the sublimable solid particles to pass trough the plate, when this one is turning. The sublimable solid particles made this way have an average diameter between 0.1 and 6 mm, in particular an average diameter between 0.15 et 4 mm. The diameter of the sublimable solid particles can be single or mixed (example: having a large part of small sublimable solid particles and a smaller part of larger sublimable solid particles). The mixed sublimable solid particles having a better cleaning effect on thick layers of dust.
The plate presents teeth made for shaving the sublimable solid material in smaller particles.
Preferably, the teeth are placed in successive lines, each line extending preferably along a radius of the plate. The plate having for example 4 or more than 4, advantageously 6 or more than 6, preferably 8 or more than 8 lines of teeth.
The teeth of the plate are advantageously situated so they shave on a different diameter of the plate. There is preferably at least one tooth on every radius of the plate, or for a major portion thereof.
According to an embodiment, the plate has at least 2 lines of teeth. The teeth of the first line, shaving on a different radius than the teeth of the second line. By placing the teeth of those lines and the inclination of the teeth, it is possible to create a centrifugal or centripetal force for the sublimable solid material at plate level.
Preferably, the plate presents at least one line of teeth, adapted to have at least one cutting line in contact with the sublimable solid material, for example defined between two flat faces making an angle of 90xc2x0 or less (for example less than 60xc2x0 even less than 45xc2x0) between them, the teeth producing sublimable particles with an irregular, but substantially spherical shape (see FIG. 17).
The driving means of the plate (i.e. the means for driving into rotation the plate) is for example a system permitting to regulate or to control the rotation speed of the plate. The rotation speed of the plate can for example be regulated or controlled between 1 round/minute and 500 rounds/minute, in particular between 5 et 100 rounds/minute, advantageously between 10 et 75 rounds/minute. The regulation of the speed can be continuous or progressive and/or discontinue or with predetermined steps. The speed of the plate will depend also of the diameter of the plate, the number of teeth, the size of the teeth, the form of the teeth, etc.
The means for preparing solid sublimable particles from the material can also be used in existing machine, such as the machine disclosed in the prior art. It means that the means for preparing solid sublimable particles, as disclosed in the system of the invention, can be associated to any means suitable for propelling the particles towards an outlet or a nozzle.
The invention relates also to a method for treating at least one face of an object by blasting sublimable particles on said face by means of a system comprising at least:
a first means for producing solid sublimable particles;
a second means connected to said first means, said second means receiving solid sublimable particles produced by said first means and propelling said solid sublimable particles towards an outlet, and
at least one duct extending between the first means and the second means for conveying solid sublimable particles produced by the first means to the second means,
in which the first means for producing solid sublimable particles comprises:
a container with a first opening adapted for receiving solid sublimable material and a second opening associated to a plate having a face intended to be directed towards the solid sublimable material present in the container and intended to be in contact with said solid sublimable material present in the container, said face being provided with at least one line of teeth associated to at least one passage extending through the plate,
means for driving into rotation the plate.
Said method comprises at least the step of:
introducing solid sublimable material in the container whereby said sublimable material contact a face of the plate provided with teeth;
driving into rotation the plate so as to extract solid sublimable particles from the solid sublimable material present in the container; said solid sublimable particles passing through the plate and falling in the duct conveying the solid sublimable particles in the second means for propelling said particles towards an outlet,
expelling solid sublimable particles from the outlet towards the object to be treated,
whereby the teeth are selected so as to form sublimable particles with an average size of less than 6 mm.
Advantageously, the solid sublimable material placed in the container is moved at least by the force of gravity, preferably substantially only by said force of gravity, towards the plate provided with teeth.
Preferably, the solid sublimable material is moved vertically in the container towards the plate.
According to an embodiment, the solid sublimable particles have an average size comprised between 0.1 and 5 mm, advantageously between 0.1 and 3 mm.
Preferably, a plate with adapted teeth is used to make sublimable solid particles with a shape with faces forming therebetween an angle or a shape edge.
For example, the solid sublimable material placed in the container is selected from the group consisting of blocs, granules, sticks, pellets and combinations thereof, said material having a size greater than 2 mm, advantageously greater than 6 mm, such as about 8 mm, 10 mm or even more.
The blocs, granules, sticks or pellets can have various average diameters from 2 mm to more than 250 mm. The sublimable solid particles made has an average diameter between 0.1 and 6 mm. The particles can be formed in one or more turns of the teeth, to let them go trough the plate.
Advantageously, we use blocs, granules, sticks or pellets containing solid CO2 to create sublimable solid particles with an average diameter inferior to 6 mm. Preferably, blocs, granules or pellets or sticks of CO2 are used. Other forms of solid CO2 material can also be used.
Preferably, a plate with adapted teeth is used to make sublimable solid particles with at least one angle or sharp edge.
Following a characteristic of an advantageous procedure of the invention, at least gravity is pushing the blocs, granules, sticks or pellets to the plate with teeth. Preferably, only gravity is pushing the blocs, sticks, granules or pellets to the plate with the teeth.
Particularities and details of the invention are explained in the detailed description below, with references to the drawings in attachment.